Method and apparatus for computing signal correlation
AssigneeGlobal Locate, Inc.
InventorsCharles Abraham, Donald L. Fuchs
Life of this patent
Estimating the term…
Abstract
A method and apparatus for computing a convolution between an input GPS signal and a C/A code reference by generating the convolution result in real time without storing unprocessed signal samples. The apparatus comprises a vector multiplier running at high speed to achieve the same result as a vector multiplier sized to process an entire epoch.
Claims23
A method for computing correlations of a digital signal with a pseudorandom reference code, where said digital signal comprises a repeating code, the method comprising:
- a) dividing a pseudorandom reference code into a plurality of code segments;
- b) selecting a code segment;
- c) forming an inner product between said selected code segment and a portion of said repeating code of said digital signal to produce a partial correlation;
- d) repeating steps b) and c) to produce a plurality of partial correlations;
- e) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations.
A receiver of global positioning system (GPS) signals comprising:
- an RF/IF converter for filtering and frequency translating received GPS signals having a repeating code to form an IF signal;
- an analog to digital converter for digitizing the IF signal;
- a tuner for removing Doppler shift from the digitized signal and producing an in-phase (I) signal and a quadrature (Q) signal;
- a decimation circuit for subsampling the I and Q signals;
- a convolution processor for producing I and Q partial correlations by multiplying selected segments of a C/A reference code with portions of said repeating code of each of said subsampled I and Q signals;
- a first accumulator for accumulating said I partial correlations to form a plurality of correlations between said I signal and the C/A reference code;
- and
- a second accumulator for accumulating said Q partial correlations to form a plurality of correlations between said Q signal and the C/A reference code.
A receiver of global positioning system (GPS) signals comprising:
- an RE/IF converter for filtering and frequency translating received GPS signals having a repeating code to form an IF signal;
- an analog to digital converter for digitizing the IF signal;
- a tuner for removing Doppler shift from the digitized signal and producing an in-phase (I) signal and a quadrature (Q) signal;
- a decimation circuit for subsampling the I and Q signals;
- a convolution processor for producing I and Q partial correlations by multiplying selected segments of a C/A reference code with portions of said repeating code of each of said subsampled I and Q signals, and further comprising a code generator for producing each C/A reference code comprising a code look up circuit and a code extender, a first shift register for storing a segment of said subsampled I signal and a second shift register for storing a segment of said subsampled Q signal, a first vector multiplier for producing I partial correlations of said subsampled I signal and a second vector multiplier for producing Q partial correlations of said subsampled Q signal;
- a first accumulator for accumulating said I partial correlations to form a plurality of correlations between said I signal and the C/A reference code;
- a second accumulator for accumulating said Q partial correlations to form a plurality of correlations between said Q signal and the C/A reference code;
- a signal normalizer for generating normalizer values representative of the magnitude or power of the I and Q signals;
- and
- magnitude accumulator for summing the normalizer values.
A method of computing correlations between a pseudorandom reference code and a digital signal having a repeating code, the method comprising:
- a) dividing a pseudorandom reference code into a plurality of code segments;
- b) selecting a portion of the repeating code of the digital signal;
- c) selecting a code segment;
- d) forming an inner product between said selected code segment and the selected portion of said repeating code to produce a partial correlation;
- e) repeating steps c) and d) to produce a plurality of partial correlations;
- f) repeating steps b) through e) for a plurality of portions of the repeating code;
- g) accumulating the plurality of partial correlations as each partial correlation is produced to form a correlation;
- and
- h) forming a plurality of correlations.
Dependencies are inferred from the claim text.